Hyaluronan (HA) is an extracellular matrix (ECM) glycosaminoglycan (GAG), which has many roles in normal tissue function and development. This includes providing support and anchorage for cells, facilitating cell-cell signaling, and facilitating cell movement and migration (Jiang D., et al., Annu. Rev. Cell Dev. Biol., 23, 435-461 (2007); Jiang, D., Liang, J. and Noble, P. W., Physiol. Rev. 91, 221-264 (2011); Laurent T. C., et al., Immunol. Cell Biol. 74, A1-7 (1996)). HA interacts with a complex network of ECM molecules that together exert decisive effects on the physical and immunologic properties of inflamed tissues (Bollyky, P. L., et al., Curr. Diab. Rep. 12, 471-480 (2012); Hull, R. L., et al., J. Histochem. Cytochem. 60, 749-760 (2012); Bogdani, M. et al., Diabetes 63, 2727-2743 (2014); Bogdani, M. et al., Curr. Diab. Rep. 14, 552-11 (2014)). In light of its central role in this network, it is believed that HA is a “keystone molecule” in the inflammatory milieu (Bollyky, P. L., et al., Curr. Diab. Rep. 12, 471-480 (2012)).
HA is a polymer of disaccharides composed of glucuronic acid and N-acetylglucosamine and linked via alternating β-1, 4 and β-1, 3 glycosidic bonds. HA can be about 25,000 disaccharide repeats in length. In vivo polymers of HA can range in size from 5,000 to 20,000,000 Da. HA is synthesized by a class of integral membrane proteins called HA synthases, of which vertebrates have three types: HAS1, HAS2, and HAS3. These enzymes lengthen HA by repeatedly adding glucuronic acid and N-acetylglucosamine to the nascent polysaccharide as it is extruded through the cell membrane into the extracellular space.
HA synthesis increases substantially at sites of inflammation (Laurent, T. C., et al., Immunol. Cell Biol. 74, A1-7 (1996)), with HA production increasing by as much as 80-fold (Laurent T. C., et al., Immunol. Cell Biol. 74, A1-7 (1996)). Increases in HA are associated with many chronic disease processes with unremitting inflammation, including type 2 diabetes (T2D) (Mine, S., et al., Endocr. J. 53, 761-766 (2006); Kang, L. et al., Diabetes 62, 1888-1896 (2013)), liver cirrhosis, asthma, and other chronic inflammatory diseases of diverse etiologies (Plevris, J. N. et al., Eur. J. Gastroenterol. Hepatol. 12, 1121-1127 (2000); Wells, A. F. et al., Transplantation 50, 240-243 (1990); Dahl, L. B., et al., Ann. Rheum. Dis. 44, 817-822 (1985); Hallgren, R., et al., Am. Rev. Respir. Dis. 139, 682-687 (1989); Evanko, S. P., et al., Am. J. Pathol. 152, 533-546 (1998); Cheng, G. et al., Matrix Biol. 30, 126-134 (2011); Ayars, A. G. et al., Int. Arch. Allergy Immunol. 161, 65-73 (2013); Liang, J. et al., J. Allergy Clin. Immunol. 128, 403-411.e3 (2011)). HA has been implicated in multiple autoimmune diseases including rheumatoid arthritis (Yoshioka Y, et al., Arthritis Rheum. 65, 1160-1170 (2013), lupus (Yung S., et al., Hindawi 2012, 207190-9 (2012)), and Hashimotos's thyroiditis (Shan, S. J. C. & Douglas, R. S., J Neuroophthalmol. 34, 177-185 (2014)). HA surrounds tumors in diverse forms of cancer (Toole, B. P., Nat. Rev. Cancer 4, 528-539 (2004)), this accumulation of HA is part of a larger pattern of ECM deposition associated with persistent inflammation.
HA increases local edema (Waldenström, A., et al., J. Clin. Invest. 88, 1622-1628 (1991) and contributes to an inflammatory cascade that drives leukocyte migration, proliferation, differentiation through effects on gene expression and cytokine production and cell survival. These pathways and the impact of HA production on innate immunity are the subject of several excellent reviews (Jiang D., et al., Annu. Rev. Cell Dev. Biol., 23, 435-461 (2007); Jiang, D., Liang, J. and Noble, P. W., Physiol. Rev. 91, 221-264 (2011); Petrey, A. C. and la Motte, de, C. A., Front Immunol. 5, 101 (2014); Slevin, M. et al., Matrix Biol. 26, 58-68 (2007); Sorokin, L., Nat. Rev. Immunol. 10, 712-723 (2010)).
Catabolic, low-molecular weight fragments of HA (LMW-HA) act as endogenous danger signals that promote antigenic responses (Termeer, C. et al., J. Exp. Med. 195, 99-111 (2002) and immune activation (Jiang, D., Liang, J. and Noble, P. W., Physiol. Rev. 91, 221-264 (2011) via CD44 and Toll-like receptor (TLR) signaling (Jiang, D. et al., Nat. Med. 11, 1173-1179 (2005); Fieber, C. et al., J. Cell. Sci. 117, 359-367 (2004); Termeer, C., et al., Trends Immunol. 24, 112-114 (2003); Taylor, K. R. et al., J. Biol. Chem. 279, 17079-17084 (2004)). LMW-HA also promotes the activation and maturation of dendritic cells (DC) (Termeer, C. et al., J. Exp. Med. 195, 99-111 (2002)), drives the release of pro-inflammatory cytokines such as IL-1β, TNF-alpha, IL-6 and IL-12 by multiple cell types (Bollyky, P. L. et al., J. Immunol. 179, 744-747 (2007); Bollyky, P. L. et al., Proc. Natl. Acad. Sci. U.S.A. 108, 7938-7943 (2011)), drives chemokine expression and cell trafficking (McKee, C. M. et al., J. Clin. Invest. 98, 2403-2413 (1996)), and promotes proliferation (Scheibner, K. A. et al., J. Immunol. 177, 1272-1281 (2006)).
Autoimmune Diseases
An autoimmune disease or disorder occurs when the body's immune system attacks and destroys healthy body tissue by mistake. Autoimmune diseases can attack almost any tissue in the body and all autoimmune diseases are characterized by local inflammation and infiltration by immune cells called lymphocytes.
As an example, autoimmune diabetes, also known as type 1 diabetes (T1D) or insulin-dependent diabetes mellitus (IDDM), occurs when the body's immune system mistakenly destroys the pancreatic cells, called beta cells, which make insulin. Damage to beta cells results in an absence or insufficient production of insulin produced by the body. In all autoimmune diseases, including autoimmune diabetes, lymphocytes migrate from the blood stream into target tissues via interactions with the extracellular matrix. In the case of autoimmune diabetes, lymphocytes attack pancreatic islets via interaction with extracellular matrix that lies between islet capillaries and endocrine cells.
One in three hundred American children will develop autoimmune diabetes. Many of these individuals can be identified before they present with hyperglycemia through screening for autoimmune diabetes associated autoantibodies. Thus, there is a therapeutic window where autoimmune diabetes could be prevented, given the knowledge and means to do so. The present disclosure describes novel strategies to reverse, ameliorate, and/or prevent the progression to autoimmune diabetes in at-risk individuals.
As an example, multiple sclerosis (MS) is also an autoimmune disease but in MS the autoimmune activity is directed against central nervous system (CNS) antigens. The disease is characterized by inflammation in parts of the CNS, leading to the loss of the myelin sheathing around neuronal axons (demyelination), axonal loss, and the eventual death of neurons, oligodendrocytes and glial cells. For a comprehensive review of MS and current therapies, see, e.g., Compston, A., et al., McAlpine's Multiple Sclerosis 4th ed., Churchill Livingstone Elsevier (2006).
MS is one of the most common diseases of the CNS in young adults, and an estimated 2.5 million people suffer from MS. MS is a chronic, progressing, disabling disease, which generally strikes its victims sometime after adolescence, with diagnosis generally made between 20 and 40 years of age, although onset can occur earlier. The disease is not directly hereditary, although genetic susceptibility plays a part in its development. MS is a complex disease with heterogeneous clinical, pathological and immunological phenotype.
There are four major clinical types of MS: 1) relapsing-remitting MS (RRMS), characterized by clearly defined relapses with full recovery or with sequelae and residual deficit upon recovery; periods between disease relapses are characterized by a lack of disease progression; 2) secondary progressive MS (SPMS), characterized by an initial relapsing remitting course followed by progression with or without occasional relapses, minor remissions, and plateaus; 3) primary progressive MS (PPMS), characterized by disease progression from onset with occasional plateaus and temporary minor improvements allowed; and 4) progressive relapsing MS (PRMS), characterized by progressive disease onset, with clear acute relapses, with or without full recovery; periods between relapses characterized by continuing progression.
Clinically, the illness most often presents as a relapsing-remitting disease and, to a lesser extent, as steady progression of neurological disability. Relapsing-remitting MS presents in the form of recurrent attacks of focal or multifocal neurologic dysfunction. Attacks can occur, remit, and recur, seemingly randomly over many years. Remission is often incomplete and as one attack follows another, a stepwise downward progression ensues with increasing permanent neurological deficit. The usual course of RRMS is characterized by repeated relapses associated, for the majority of patients, with the eventual onset of disease progression. The subsequent course of the disease is unpredictable, although most patients with a relapsing-remitting disease will eventually develop secondary progressive disease. In the relapsing-remitting phase, relapses alternate with periods of clinical inactivity and may or may not be marked by sequelae depending on the presence of neurological deficits between episodes. Periods between relapses during the relapsing-remitting phase are clinically stable. On the other hand, patients with progressive MS exhibit a steady increase in deficits as defined above and either from onset or after a period of episodes, but this designation does not preclude the further occurrence of new relapses.
In healthy individuals (i.e., those without an autoimmune disease or disorder), immune tolerance is maintained by populations of regulatory T-cells including FoxP3+ regulatory T-cells (Treg) (Sakaguchi, S., et al., Nat. Rev. Immunol. 10, 490-500 (2010)). Treg absence or depletion leads to multi-systemic autoimmunity, including autoimmune diabetes, in mice and humans (Wildin, R. S., et al., Nat. Genet. 27, 18-20 (2001)) whereas adoptive transfer of Treg can abrogate autoimmunity. In MS, Treg present in the CNS are known to limit the extent of neuroinflammation and to facilitate clinical recovery during the mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), such that multiple investigative therapeutic strategies to treat autoimmune demyelination are directed at promoting the number and/or function of Treg.
There is a need for developing tools to induce Foxp3+ Treg because of their ability to suppress inflammation, including autoimmunity (Sakaguchi, S., et al., Nat. Rev. Immunol. 10, 490-500 (2010)) but also other inflammatory diseases, including T2D (Eller, K. et al., Diabetes 60, 2954-2962 (2011)). However, existing therapies have not managed to induce stable, functional FoxP3+ Treg. This is in part because Treg in vivo are a population in flux. Natural Treg (nTreg) continually emerge through thymic selection, whereas induced Treg (iTreg) originate in peripheral tissues in response to inflammatory stimuli and can revert into effector T-cells. This variability in the number and function of local Treg at sites of inflammation can impact the durability of immune tolerance in peripheral tissues.
Despite the fact that the inflammatory milieu is known to have decisive effects on immune tolerance, little is known about how the tissue micro-environment influences the function and number of Treg. Therefore, there is increasing interest in the role of ECM at the interface between lymphocytes and local cells in autoimmunity (Bollyky, P. L., et al., Curr. Diab. Rep. 12, 471-480 (2012); Hull, R. L., et al., J. Histochem. Cytochem. 60, 749-760 (2012); Irving-Rodgers, H. F. et al., Diabetologia 51, 1680-1688 (2008); Ziolkowski, A. F., et al., J. Clin. Invest. 122, 132-141 (2012)).
HA in Autoimmune and Inflammatory Diseases.
HA is produced by a variety of cell types in response to inflammatory stimuli including hyperglycemia (Shakya, S., et al., Int. J. Cell Biol. 2015, 701738-11 (2015); Wang, A. and Hascall, V. C., Autophagy 5, 864-865 (2009)), inflammatory cytokines (Bollyky, P. L. et al., Cell. Mol. Immunol. 7, 211-220 (2010)), and other triggers (Lauer, M. E. et al., J. Biol. Chem. 284, 5299-5312 (2009)). The HA present within inflamed tissues functions as an endogenous “danger signal” (Noble, P. W., Matrix Biol. 21, 25-29 (2002)) and promotes inflammatory responses (Jiang, D., Liang, J. and Noble, P. W., Physiol. Rev. 91, 221-264 (2011); la Motte, de, C. et al., Am. J. Pathol. 174, 2254-2264 (2009)).
HA is highly abundant within chronically inflamed tissues including for example MS lesions (Back, S. A. et al., Nat. Med. 11, 966-972 (2005)). For example, in one study HA was shown to accumulate in demyelinated lesions in MS and EAE. Immunostaining for proteolipid protein (PLP) of a chronic MS lesion showed complete loss of myelin in the center of the lesions. CD44 staining revealed high levels of CD44 in the lesions, and elevated CD44 expression in GFAP-expressing reactive astrocytes were also found. HA staining showed high levels of HA in demyelinated regions of the lesions but at lower levels in the lesion borders (Back, S. A. et al., Nat. Med. 11, 966-972 (2005)).
Typically, HA present within chronically inflamed tissues takes the form of short, highly catabolized fragments (as reviewed in Bollyky, P. L., et al., Curr. Diab. Rep. 12, 471-480 (2012)) that are pro-inflammatory agonists of Toll-like receptor signalling (Jiang, D., Liang, J. and Noble, P. W., Physiol. Rev. 91, 221-264 (2011); Laurent, T. C., et al., Immunol. Cell Biol. 74, A1-7 (1996)), driving dendritic cell maturation, and promoting phagocytosis (Termeer, C. et al., J. Exp. Med. 195, 99-111 (2002); Jiang, D. et al., Nat. Med. 11, 1173-1179 (2005)). HA overexpression tends to drive inflammation (Olsson, M., et al., PLOS Genetics 7, e1001332 (2011)) presumably through production of increased HA fragments, while inhibition of HA synthesis, including treatment with 4-methylumbelliferone (4-MU, Hymecromone), tends to reduce inflammation (Yoshioka, Y. et al., Arthritis Rheum. 65, 1160-1170 (2013); McKallip, R. J., et al., Inflammation 38, 1250-1259 (2015); Colombaro, V. et al., Nephrol. Dial. Transplant. 28, 2484-2493 (2013)). With respect to the role of HA in local immune modulation, it is known that low molecular weight HA fragments inhibit the function of FoxP3+ Treg (Bollyky, P. L. et al., J. Immunol. 179, 744-747 (2007); Bollyky, P. L. et al., J. Immunol. 183, 2232-2241 (2009)). These effects are mediated via TLR signaling and via interactions with the HA receptor CD44.
In the healthy CNS, astrocytes are the main producers of low levels of HA, depositing it as ECM complexes in the spaces between myelinated axons and between myelin sheaths and astrocyte processes (Asher, R., et al., J. Neurosci. Res. 28, 410-421 (1991)). Upon injury, however, reactive astrocytes produce abundant amounts of HA, which accumulate in damaged areas (Back, S. A. et al., Nat. Med. 11, 966-972 (2005); Bugiani, M. et al., Brain 136, 209-222 (2013)). As such, HA is present at high levels in demyelinating lesions in MS patients and in mice with EAE (Back, S. A. et al., Nat. Med. 11, 966-972 (2005)).
Recently, it was shown that HA deposits accumulate within the pancreatic islets of individuals with recent-onset T1D (Bogdani, M. et al., Diabetes 63, 2727-2743 (2014)). These deposits were present at sites of insulitis (Bogdani, M. et al., Diabetes 63, 2727-2743 (2014)). Similar HA deposits were observed in animal models of T1D (Nagy, N. et al., J. Clin. Invest. 125, 10.1172/JCI79271-0 (2015)).
Many other chronic inflammatory diseases are also associated with HA deposition. For example, the pathogenesis of T2D is known to have an inflammatory component with inflammation localized to the muscle and adipose tissue (Wellen, K. E. and Hotamisligil, G. S., J. Clin. Invest. 115, 1111-1119 (2005)). In T2D HA deposition has been noted in skeletal muscle (Kang, L. et al., Diabetes 62, 1888-1896 (2013)), adipose tissue (Liu, L. F. et al., Diabetologia 58, 1579-1586 (2015)), and other tissues of obese and diabetic animals (Mine, S., et al., Endocr. J. 53, 761-766 (2006); Bowling, F. L., et al., Nat Rev Endocrinol. 11, 606-616 (2015); Dalferes, E. R., et al., Proc. Soc. Exp. Biol. Med. 148, 918-924 (1975); Dwyer, T. M. et al., Kidney Int. 58, 721-729 (2000); Zhu, Y., et al., Sci. Transl. Med 8, 323ps4-323ps4 (2016)). As another example many cancers are also associated with abundant HA in the matrix surrounding tumors (Li, Y. and Heldin, P., Br. J. Cancer 85, 600-607 (2001); Schwertfeger, K. L., et al., Front. Immunol. 6, 236 (2015)).
HA Synthesis Inhibitors
4-MU is a selective inhibitor of HA synthesis. The compound was first used in vitro in 1990 by Nakamura et al., to inhibit HA-synthesis in skin fibroblasts (Nakamura, T. et al., Biochem. Biophys. Res. Commun. 172, 70-76 (1990)). In 2004, the mechanism of 4-MU was discovered by Kakizaki et al., and since then it has been used in in vivo studies in mice and rats to investigate the 4-MU influence, mainly in cancer studies (Kakizaki, I. et al., J. Biol. Chem. 279, 33281-33289 (2004)); see also, e.g., Yoshihara, S. et al., FEBS Lett. 579, 2722-2726 (2005); Lokeshwar, V. B. et al., Cancer Res. 70, 2613-2623 (2010) and in atherosclerosis studies (Nagy, N. et al., Circulation 122, 2313-2322 (2010)). 4-MU is also already used in humans. It is available without a prescription as Heparvit, a nutraceutical product for cancer patients. Furthermore, it is available with prescription in Europe and Asia to treat biliary spasm under the name Hymecromone. In that setting, the drug has an excellent safety profile and has been used for several years.
One strategy to decrease or prevent the pro-inflammatory activity of LMW-HA within autoimmune lesions is to limit HA synthesis using 4-MU. 4-MU is a derivate that belongs to the coumarin family. Other coumarin derivatives, such as phenprocoumon (Marcumar®) and warfarin (Coumadin®), are used in preventive medicine to reduce cardiovascular events due to their anticoagulatory mechanism. 4-MU is thought to inhibit HA production in at least two ways. First, 4-MU is thought to function as a competitive substrate for UDP-glucuronyltransferase (UGT), an enzyme involved in HA synthesis (Kakiazaki, I., et al., J. Biol. Chem. 279, 33281-33289 (2004)). HA is produced by the HA synthases HAS1, HAS2 and HAS3 from the precursors UDP-glucuronic acid (UDP-GlcUA) and UDP-N-acetyl-glucosamine (UDP-GlcNAc). These are generated by the transfer of an UDP-residue to N-acetylglucosamine and glucuronic acid via the UDP-glucuryltransferase (UGT). The availability of UDP-GlcUA and UDP-GlcNAc thereby control HA synthesis (Vigetti, D. et al., J. Biol. Chem. 281, 8254-8263 (2006)). In the presence of 4-MU, it covalently binds through its hydroxyl group at position 4 to glucuronic acid via the UGT. As a consequence, the concentration of UDP-glucuronic acid declines in the cytosol and HA synthesis is reduced. This therewith reduces 4-MU the UDP-GlcUA content inside the cells. 4-MU inhibits HA synthesis by depleting the HAS enzyme UDP-GlcUA, which is consumed by 4-MU glucuronidation. So far it is unclear how exactly the second mechanism works, but, 4-MU reduces expression of HAS mRNA expression (Kultti A., et al., Exp. Cell Res. 315, 1914-1923 (2009) as well as mRNA for UDP glucose pyrophosphorylase and dehydrogenase (Vigetti, D. et al., Glycobiology 19, 537-546 (2009)).
A few studies have investigated the impact of 4-MU on HA synthesis in autoimmunity and inflammation. 4-MU has been used to inhibit HA production by several human pathogens and their interactions with human cells in vitro (Jong, A. et al., Eukaryotic Cell 6, 1486-1496 (2007); Kakizaki, I. et al., Eur. J. Biochem. 269, 5066-5075 (2002)). In vivo studies showed that 4-MU treatment decreased or prevented lung injury and reduced inflammatory cytokine levels in mouse models of staphylococcal enterotoxin-mediated (McKallip, R. J., et al., Toxins (Basel) 5, 1814-1826 (2013)) and lipopolysaccharide-mediated acute lung injury (McKallip, R. J., et al., Inflammation 38, 1250-1259 (2015)). 4-MU has also been shown to have protective effects on non-infectious inflammation, including renal ischemia and reperfusion (Colombaro, V. et al., Nephrol. Dial. Transplant. 28, 2484-2493 (2013)), and airway inflammation secondary to cigarette smoke, 4-MU also restores normoglycemia and promotes insulin sensitivity in obese, diabetic mice via increased production of adiponectin (Sim, M.-O., et al., Chem. Biol. Interact. 216, 9-16 (2014)). 4-MU has also been reported to ameliorate disease in a limited number of mouse models of autoimmune disease. Specifically, 4-MU treatment was beneficial in the collagen-induced arthritis model where it improved disease scores and reduced expression of matrix metaloproteases (MMPs) (Yoshioka Y, et al., Arthritis Rheum. 65, 1160-1170 (2013)). More recently, 4-MU treatment was demonstrated to prevent and treat disease in the experimental autoimmune encephalomyelitis (EAE) model where it increased populations of regulatory T-cells and polarized T-cell differentiation away from pathogenic, T-helper 1 T-cell subsets and towards non-pathogenic T-helper 2 subsets (Mueller, A. M., et al., J. Biol. Chem. 289, 22888-22899 (2014)). In addition, 4-MU treatment reduced the number of tumor satellites, inhibited angiogenesis and cell growth in tumors (Yoshihara, S. et al., FEBS Lett. 579, 2722-2726 (2005); Lokeshwar, V. B. et al., Cancer Res. 70, 2613-2623 (2010); Garcia-Vilas, J. A., et al., J. Agric. Food Chem. 61, 4063-4071 (2013)). The existing in vitro and in vivo data suggest that hymecromone can have utility as a component of therapeutic regimens directed against HA-producing cancers.
4-MU treatment has been reported to reduce or prevent cell-cell interactions required for antigen presentation (Bollyky, P. L. et al., Cell. Mol. Immunol. 7, 211-220 (2010)) and has been described to have inhibitory effects on T-cell proliferation (Mahaffey, C. L. and Mummert, M. E., J. Immunol. 179, 8191-8199 (2007); Mummert, M. E. et al., J. Immunol. 169, 4322-4331 (2002)). These effects are consistent with established roles for HA and its receptors in T-cell proliferation, activation, and differentiation (Jiang, D., Liang, J. and Noble, P. W., Physiol. Rev. 91, 221-264 (2011); Guan, H., et al., J. Immunol. 183, 172-180 (2009); Ponta, H., et al., Nat. Rev. Mol. Cell Biol. 4, 33-45 (2003)). There are also indications that 4-MU treatment can make some models of inflammation worse. 4-MU treatment was associated with worse atherosclerosis in ApoE-deficient mice fed a high-fat diet (Nagy, N. et al., Circulation 122, 2313-2322 (2010)).
4-MU treatment has been reported to limit the progression of EAE (Mueller, A. M., et al., J. Biol. Chem. 289, 22888-22899 (2014); Kuipers, H. F. et al., Proc. Natl. Acad. Sci. U.S.A. 113, 1339-1344 (2016)) and autoimmune diabetes in both the DORmO and NOD mouse models (Nagy, N. et al., J. Clin. Invest. 125, 10.1172/JCI79271-0 (2015); Kuipers, H. F. et al., Clin. Exp. Immunol. 185, 372-381 (2016)). This therapeutic effect was not only a result of the polarization of the T-cell response away from a pathogenic Th1 response, but also the reduction of infiltration of these cells into sites of autoimmune attack. Additionally, because 4-MU treatment lifts the inhibition of FoxP3+ Treg induction and function by LMW-HA, this inhibition of the pathogenic response is aided by an increase of Treg numbers (Nagy, N. et al., J. Clin. Invest. 125, 10.1172/JCI79271-0 (2015); Kuipers, H. F. et al., Proc. Natl. Acad. Sci. U.S.A. 113, 1339-1344 (2016); Kuipers, H. F. et al., Clin. Exp. Immunol. 185, 372-381 (2016)). Furthermore, in addition to sustaining a pro-inflammatory environment in MS lesions, HA deposits have been show to inhibit the maturation of oligodendrocytes, the myelin forming cells of the CNS, in MS and other myelin degenerative disorders, and as such are thought to prevent repair of myelin, further contributing to MS pathogenesis (Back, S. A. et al., Nat. Med. 11, 966-972 (2005); Bugiani, M. et al., Brain 136, 209-222 (2013)). 4-MU treatment can restore the HA load in inflamed tissues to a dominance of anti-inflammatory high molecular weight (HMW) polymers.
Since more and more studies highlight the role of HA in inflammation, autoimmunity, and cancer, there has been great interest in identifying pharmacologic tools to inhibit HA synthesis. 4-MU has been shown to inhibit HA production in multiple cell lines and tissue types both in vitro and in vivo (Nagy, N. et al., Circulation 122, 2313-2322 (2010); Kakiazaki, I., et al., J. Biol. Chem. 279, 33281-33289 (2004); Kultti A., et al., Exp. Cell Res. 315, 1914-1923 (2009); Bollyky, P. L. et al., Cell. Mol. Immunol. 7, 211-220 (2010)), and has received much attention as a potential therapeutic in inflammation, autoimmunity and cancer (Nagy, N. et al., Front Immunol. 6, 123 (2015)), unrelated to its clinical use for bile duct disorders (Abate, A. et al., Drugs Exp. Clin. Res. 27, 223-231 (2001)). Unfortunately, 4-MU has poor pharmacokinetics and limited bioavailability outside the liver and biliary tract (Nagy, N. et al., Front Immunol. 6, 123 (2015); Garrett, E. R., et al., Biopharm Drug Dispos 14, 13-39 (1993); Garrett, E. R. and Venitz, J., J. Pharm. Sci. 83, 115-116 (1994)).
There is a need for HA synthesis inhibitors that can provide a safe and effective therapy for, for example, autoimmune diseases such as, for example, diabetes and MS and for inflammatory disorders, such as, for example, diabetes and cancer. The present disclosure seeks to fulfill these needs and provides further related advantages.